Direct observation of receptors and images in simple and compound eyes.
The relation between the quality of the optical image and the fineness of the retinal mosaic has been studied in eyes of three different optical types: the simple eyes of spiders, the superposition compound eyes of moths, and the apposition compound eyes of butterflies. In all three it is possible to observe both the receptor mosaic and the image in the living eye, using appropriate ophthalmoscopic techniques. Whereas in humans the retinal sampling frequency approaches the optical cut-off frequency quite closely, in diurnal insects of both types the image is undersampled by a factor of 2-3, and in crepuscular spiders this factor may be greater than 100. Reasons for these differences are discussed.
Land
M F
MF
School of Biological Sciences, University of Sussex, Brighton, U.K.
D000818:Animals; D002080:Butterflies / Q000033:anatomy & histology*; D009036:Moths / Q000033:anatomy & histology*; D009887:Ophthalmoscopy; D055095:Optics and Photonics; D010786:Photoreceptor Cells / Q000033:anatomy & histology* / Q000502:physiology; D013112:Spiders / Q000033:anatomy & histology*; D014785:Vision, Ocular / Q000502:physiology